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CVE-2026-89795
PCI: Allow per function PCI slots to fix slot reset on s390
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/pci. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89795 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6568-1 · 2026-10-16 · text | 6.12.113-1 | Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
On s390 systems, which use a machine level hypervisor, PCI devices are always accessed through a form of PCI pass-through which fundamentally operates on a per PCI function granularity. This is also reflected in the s390 PCI hotplug driver which creates hotplug slots for individual PCI functions. Its reset_slot() function, which is a wrapper for zpci_hot_reset_device(), thus also resets individual functions. Currently, the pci_create_slot() assigns the same pci_slot object to multifunction devices. This approach worked fine on s390 systems that only exposed virtual functions as individual PCI domains to the operating system. Since commit 44510d6fa0c0 ("s390/pci: Handling multifunctions") s390 supports exposing the topology of multifunction PCI devices by grouping them in a shared PCI domain. This creates a problem when resetting a function through the hotplug driver's slot_reset() interface. When attempting to reset a function through the hotplug driver, the shared slot assignment causes the wrong function to be reset instead of the intended one. It also leaks memory as we do create a pci_slot object for the function, but don't correctly free it in pci_slot_release(). Add a flag for struct pci_slot to allow per function PCI slots for functions managed through a hypervisor, which exposes individual PCI functions while retaining the topology. Since we can use all 8 bits for slot 'number' (for ARI devices), change slot 'number' u16 to account for special values PCI_SLOT_PLACEHOLDER and PCI_SLOT_ALL_DEVICES.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/pci/pci.c
drivers/pci/slot.c
include/linux/pci.h
- What this is
- PCI SUBSYSTEMMAINTAINERS section matched on drivers/pci/ · linux-pci@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_PCI /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixieYnot built on armel/rpi
- forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_PCI
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/pci
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.8 | 6.12.112 | 0d1a7d67f456 |
| 5.8 | 6.18.52 | 2050d900f9ad |
| 5.8 | 7.2.5 | ecdcceed4d37 |
| 5.8 | 7.3 | dcc5bec09e23 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6568-1 | 2026-10-16 | trixie 6.12.113-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The flaw is reached from local PCI reset paths (sysfs device reset, VFIO_DEVICE_RESET, and vfio_pci_core_enable()) that call pci_try_reset_function() -> pci_dev_reset_slot_function() -> s390 reset_slot()/zpci_hot_reset_device(); there is no network or adjacent-radio path.
- AC:LAttack complexity, low
- On s390 multifunction domains pci_create_slot() matches PCI_SLOT(devfn) against a full 8-bit slot number, so siblings/VFs are assigned the wrong pci_slot and a reset deterministically invokes the other function's hotplug reset_slot() with no race or attacker-uncontrollable layout.
- PR:LPrivileges required, low
- vfio_pci_core_enable() and VFIO_DEVICE_RESET call pci_try_reset_function() with no capable() check on the IOMMU path; IBM Z/LinuxONE SR-IOV VF passthrough routinely grants that VFIO fd to an unprivileged qemu/tenant user rather than init-namespace root.
- UI:NUser interaction, none
- The attacker opens the assigned VFIO device or issues VFIO_DEVICE_RESET themselves; prior admin binding of the zPCI function to vfio-pci is deployment configuration, not victim interaction.
- S:CScope, changed
- Function reset uses the wrongly shared pci_slot and issues zpci_hot_reset_device() on a sibling/PF outside the caller's VFIO device set, bypassing VFIO's slot-wide membership check and crossing zPCI per-function isolation into host or other-tenant devices.
- C:NConfidentiality impact, none
- This is a wrong-function hardware reset plus a pci_slot lifetime leak; it does not perform an out-of-bounds read, use-after-free, or other disclosure of kernel or other users' memory.
- I:HIntegrity impact, high
- zpci_hot_reset_device() disable/re-enable of the unintended function wipes that function's hardware state behind its owner's driver, destroying in-flight I/O and device configuration on a host PF or another tenant's NIC/storage function.
- A:HAvailability impact, high
- Surprise reset of an in-use PF or sibling denies that device and all VFs behind it, and can oops the bound host driver which continues MMIO against a freshly reset zPCI function, causing host kernel availability loss.